The vector \(f_c\)  encoding the cardinality of objects in each category, is obtained from the pre-computed object information (category and number) from YOLOv3 without the need to perform object detection online.
To incorporate scene information we use a pre-trained ResNet-50, referred to as Places365, on scene recognition, that classifies images in 365 pre-defined scene categories [1]}. We add a fully-connected layer before the final softmax layer of the ResNet-50 model to compress the output into two categories and use the output logits as scene information.
